1. Field of the Invention
The present invention relates to lip seals, and more particularly to a Uni-Directional polytetrafluoroethylene (PTFE) seal for one direction of shaft rotation.
2. Description of Related Art
Lip seals have been known for years and have been found in applications when an internal seal is needed to seal off fluid with the shaft rotating in only one direction. Generally, the fluid is confined within a chamber and it is the function of the lip seal to prevent the fluid from leaking via the annular space between the interior chamber wall and the shaft. The lip seals are commonly used for sealing automotive engine crankshafts, transmission shafts, pump shafts and any other type of shaft which has a fluid/air barrier. The lip seals are generally maintained in continuous contact with a rotating shaft and have the characteristics of pumping fluid which comes in contact with the seal back towards the fluid chamber being sealed.
Many prior art seals used to control uni-directional fluid flow have been made of molded rubber. However, these rubber seals suffer from defects such as thermal embrittlement or other forms of material degradation, and do not have the ability to resist wear for long periods with sparse lubrication and have a high co-efficient of friction.
Therefore, there is a need in the art for a uni-directional PTFE seal to overcome the problems with the previous rubber lip uni-directional seals and PTFE seals that have trouble with static leakage and are not properly lubricated due to their pumping features.